Large, phased-array antennas are often used in spacecraft to support a variety of operations such as reconnaissance missions, collecting radar images, tracking ground-based and air-based targets, and providing high bandwidth communications. There are also plans to use phased-array antennas on high altitude airships and other unmanned platforms. The large, phased-array antennas are made up of a large plurality of independent antenna elements including transmit/receive modules, phase shifters and other elements. Traditionally, the surfaces forming the phased-array antenna had to be maintained very flat or the distortion in the antenna surface had to be known to within a very small fraction of the wavelength corresponding to the operational frequency of the antenna (e.g., one-thirtieth of the wavelength for space-based radar at 10 GHz=1 mm flatness tolerance) in order for the antenna to perform correctly. For example, for space-based RADAR (SBR) applications, a very high degree of surface planarity had to be maintained to enable the effective use of ground clutter suppression algorithms. A high degree of surface planarity was also critical for space-based optics applications and for ground moving target tracking applications. Moreover, a large phased array must be “electrically flat”, meaning that electrical components operate on the same schedule (i.e., have the same time constants, be initialized and fired at the same instant, etc.) Even slight latencies or other discrepancies in the operating response of one element with respect to its neighbors, can make an otherwise mechanically flat array appear distorted.
Conventional phased-array antennas achieve this required flatness by using centralized timing signals and high stiffness structural designs (i.e., trusses) that add significant weight and volume to the antenna when it is stowed in a launch vehicle. As can be appreciated, as the antenna area increases, the stowed volume of the array limits the antenna size due to the restrictions imposed by the launch vehicle fairing within which the stowed antenna must fit. A large-scale array antenna (whether for use as radar or any other application) cannot achieve acceptably low structural weight without significant relaxation of planar structural rigidity. This is especially true of an antenna mounted to an airship or other air vehicle. Less rigid antennas will characteristically exhibit a wide spectrum of aero-elastic modes, thereby introducing errors to the signals and reducing the effectiveness of the antennas.